1. Field of the Invention
The invention relates to a defoamer preparation as well as to a process for the production of the preparation.
2. Description of the Prior Art
It is well known that defoamer preparations can be produced from water-insoluble defoamer oils, water-soluble emulsifiers and finely divided silica. German Offenlegungsschrift No. 24 43 853 is an example of a disclosure showing the state of the art. This Offenlegungsschrift relates to a preparation for defoaming aqueous solutions and dispersions and contains organosilicon compounds and fillers, characterized by the fact that it consists of 0.2 to 7.5 weight % of highly dispersed silica or high dispersed aluminum oxide and
92.5 to 99.8 weight % of a methylpolysiloxane-polyoxyalkylene block copolymer, which contains 10 to 60 weight % of methylpolysiloxane and whose polyoxyalkylene block has more than 80 to 100 weight % propylene oxide units.
At the same time, 2 to 10 weight % of the block copolymer can be replaced by nonionic emulsifiers, which have an average HLB value of 8 to 14. The function of the water-insoluble defoamer oil is taken over by the so-called methylpolysiloxane-polyoxyalkylene block copolymer. The nonionic emulsifiers mentioned serve as water-soluble emulsifiers.
German Offenlegungsschrift No. 23 45 335 relates to a preparation for defoaming aqueous solutions or dispersions, characterized by a content of 80 to 95 weight % of a mineral oil or a vegetable or animal oil, 1 to 7.5 weight % of a highly dispersed silica or a highly dispersed aluminum oxide. It further contains 1.0 to 10 weight % of a methylpolysiloxanepolyoxyalkylene block copolymer which contains 10 to 60 weight % of methylpolysiloxane and whose polyoxyalkylene block has 80 to 100 weight % of propylene oxide units. Optionally, the preparation may contain 2 to 10 weight % of nonionic emulsifiers whose average HLB value is 8 to 14, the sum of the aforementioned components adding up to 100 weight %.
As the water-insoluble defoamer oils, combinations of mineral oils, vegetable or animal oils, and water-insoluble methylpolysiloxane-polyoxyalkylene block copolymers are used.
However, it turns out that the water-insoluble defoamer oils frequently are not miscible with the water-soluble emulsifiers and it is impossible or difficult to prepare dispersions of both constituents which are stable over a period of days or weeks.